General Science - Physics MCQs
Physics Objective (Multiple Choice) General Knowledge & General Science Questions & Answers for SSC-CGL, UPPSC, UPSC, NDA, CDS and UPSC Civil Services Prelims Examinations.
71. What is the time taken by two consecutive compressions or rarefactions to cross a fixed point in a sound wave known as?
[A] Amplitude
[B] Time period
[C] Angular Frequency
[D] Angular Displacement
Show Answer
Correct Answer: B [Time period]
Notes:
The time taken by two consecutive compressions or rarefactions to cross a fixed point is called the time period of the wave.
72. What is the measure of the response of the ear to the sound known as?
[A] Pitch
[B] Intensity
[C] Loudness
[D] Amplitude
Show Answer
Correct Answer: C [Loudness]
Notes:
Loudness is a measure of the response of the ear to the sound. Even when two sounds are of equal intensity, we may hear one as louder than the other simply because our ear detects it better.
73. In which of the following mediums will sound travel with greater speed at 0° C?
[A] Aluminium
[B] Water
[C] Hydrogen
[D] Same in all of the above
Show Answer
Correct Answer: A [Aluminium]
Notes:
The speed of sound decreases when we go from solid to gaseous state.
74. Which of the following is correct about the speed of the sound, at same temperature?
[A] sound travels faster in humid air than in dry air
[B] sound travels slower in humid air than in dry air
[C] speed of sound is same in humid air and dry air
[D] None of the above
Show Answer
Correct Answer: A [sound travels faster in humid air than in dry air]
Notes:
With increase in humidity, density of air decreases. So with rise in humidity velocity of sound increases. This is why sound travels faster in humid air (rainy season) than in dry air (summer) at the same temperature.
75. What is the S.I. unit of absorptive power?
[A] dioptre
[B] metre
[C] ampere
[D] No unit
Show Answer
Correct Answer: D [No unit]
Notes:
Since absorptive power is a pure ratio it has no units and dimensions.
76. What is the S.I unit of specific heat capacity?
[A] J kg-2 K-1
[B] J kg-1 K1
[C] J kg-1 K-2
[D] J kg-1 K-1
Show Answer
Correct Answer: D [J kg-1 K-1]
Notes:
The specific heat capacity is the property of the substance which determines the change in the temperature of the substance (undergoing no phase change) when a given quantity of heat is absorbed (or given off) by it. The SI unit of specific heat capacity is J kg 1 K– 1.
77. What is the triple point of water?
[A] Temperature = -273.16 K, pressure= 6.11×10-6Pa
[B] Temperature = -273.16 K, pressure= 6.11×10-3 Pa
[C] Temperature = 273.16 K, pressure= 6.11×10-6 Pa
[D] Temperature = 273.16 K, pressure= 6.11×10-3 Pa
Show Answer
Correct Answer: D [Temperature = 273.16 K, pressure= 6.11×10-3 Pa]
Notes:
The triple point of water is represented by the temperature 273.16 K and pressure 6.11×10-3 Pa.
78. What is the S.I unit of Stefan-Boltzmann constant?
[A] 2.34 × 10–4 W m–2 K–4
[B] 1.44 × 10–6 W m–2 K–4
[C] 3.99 × 10–7 W m–2 K–4
[D] 5.67 × 10–8 W m–2 K–4
Show Answer
Correct Answer: D [5.67 × 10–8 W m–2 K–4]
Notes:
The value of Stefan-Boltzmann constant in SI units is 5.67 × 10–8 W m–2 K–4.
79. Which of the following is true about a cyclic process?
[A] the total heat absorbed equals the work done by the system.
[B] the system returns to its initial state
[C] Both a and b
[D] None
Show Answer
Correct Answer: C [Both a and b]
Notes:
In a cyclic process, the system returns to its initial state and the total heat absorbed equals the work done by the system.
80. What is the S.I. unit of power of a lens?
[A] metre
[B] watt
[C] dioptre
[D] second
Show Answer
Correct Answer: C [dioptre]
Notes:
The SI unit of power of a lens is ‘dioptre’. It is denoted by the letter D. If f is expressed in metres, then, power is expressed in dioptres.
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